[PATCH net-next] net: phy: motorcomm: enable the reference clock for YT8531

[Jiaxing Hu <gahing@gahingwoo.com>]

The YT8531 needs a 25 MHz reference. On boards without a local crystal
it is fed from the SoC, described as a clock on the PHY node. Get and
enable it in probe so the PHY is clocked before its registers are
accessed. The clock is optional, so crystal-clocked boards are
unaffected.

Signed-off-by: Jiaxing Hu <gahing@gahingwoo.com>
---
This supersedes "[PATCH net-next v2] net: stmmac: dwmac-rk: ..." which
enabled the clock on the MAC side; Andrew and Maxime rightly pointed out
that the PHY is the consumer and should enable it. That series is dropped.

The DTS that consumes this (rk3576-armsom-cm5) goes to the rockchip tree
separately; the clock is optional so this patch stands alone. Tested on
an ArmSoM CM5-IO: the YT8531 links at 1000 Mbit/s.
 drivers/net/phy/motorcomm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/phy/motorcomm.c b/drivers/net/phy/motorcomm.c
index 708491bc1..2f85974a3 100644
--- a/drivers/net/phy/motorcomm.c
+++ b/drivers/net/phy/motorcomm.c
@@ -6,6 +6,7 @@
  * Author: Frank <Frank.Sae@motor-comm.com>
  */
 
+#include <linux/clk.h>
 #include <linux/etherdevice.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -1169,9 +1170,20 @@ static int yt8521_probe(struct phy_device *phydev)
 static int yt8531_probe(struct phy_device *phydev)
 {
 	struct device *dev = &phydev->mdio.dev;
+	struct clk *clk;
 	u16 mask, val;
 	u32 freq;
 
+	/*
+	 * A crystal-less YT8531 takes its 25 MHz reference from the SoC. When
+	 * that reference is described as a clock, enable it for the life of the
+	 * device. It is optional, so crystal-clocked boards are unaffected.
+	 */
+	clk = devm_clk_get_optional_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk),
+				     "failed to get and enable the reference clock\n");
+
 	if (device_property_read_u32(dev, "motorcomm,clk-out-frequency-hz", &freq))
 		freq = YTPHY_DTS_OUTPUT_CLK_DIS;
 
-- 
2.43.0